Oxidizer comprising water, magnesium nitrate, and methanol



Oct. 13, 1964 L. GREINER 3,152,937

OXIDIZER COMPRISING WATER, MAGNESIUM NITRATE AND METHANOL Filed June 13, 1958 3 Sheets-Sheet 1 91' a ,L 5 R1./ A A L NQ m u N gnu :ilh m iiili g Si l N Q;

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29, 3 M q 2 H1 I 8 1' 8 ii: 8 I |l| 3 g Q I 32 IN VENTOR LEONARD GREINER ATTORNEYS Oct. 13, 1964 L. GREINER 3,152,937

OXIDIZER COMPRISING WATER, MAGNESIUM NITRATE AND METHANOL Filed June 15, 1958 3 Sheets-Sheet 2 Y Y L "MAA 3YAVAV5YAWAYAVAVAYA AVAK AV 2 V YAYAY W0 H2O CH3QH INVENTOR LEONARD GREINER p fwaz'sw ATTORNEYS Oct. 13, 1964 M 1.. GREINER 3,152,937

OXIDIZER COMPRISING WATER, MAGNESIUM NITRATE AND METHANOL Filed June 13, 1958 5 Sheets-Sheet 3 H2O X CH3OH INVENT OR LEONARD gRgINER fw /7 M BY ATTORNEYS United States Patent 3,152,937 OXIDIZER 'CGMPRISING WATER, MAGNESKUM NITRATE, AND METHANOL Leonard Greiner, Richmond, Va, assignor to Texaco Experiment Incorporated, a corporation of Virginia Filed June 13, 1558, Ser. No. 741,972 3 Claims. (Ci. 14-9-22) This invention relates to a fuel system and particularly to liquid propellant oxidizers for light-metal fuels having utility as rocket propellants.

It is an object of the invention to provide a fuel system with a high density impulse that is relatively simple and cheap to manufacture, has excellent storage properties and has unusually safe handling characteristics.

A further object is to provide a liquid oxidizer for a rocket-propellant system wherein the fuel comprises a light metal and the oxidizer has a low freezing point, high density, and is relatively non-injurious to tissue and very stable.

These and other objects and advantages are provided by a fuel system comprising as a fuel at least one metal selected from the group consisting of magnesium, aluminum, lithium and boron and an oxidizer comprising a solution of methanol, water and either magnesium nitrate or aluminum nitrate.

The invention will be more particularly described with reference to the illustrative embodiments shown in the accompanying drawings wherein:

FIG. 1 is a sectional view of a rocket employing the fuel system of the present invention;

FIG. 2 is a phase diagram for the system magnesium nitrate-water-methanol; and

FIG. 3 is a phase diagram for the system aluminum nitrate-water-methanol.

It has been the constant endeavor of rocket propulsion engineers to devise a safe and stable liquid propellant system for use in rockets, since liquid propellants are relatively cheap and easy to manufacture and, being liquid, are adaptable to thrust control simply by adjusting a valve or similar device that controls their rates of flow into the combustion chamber. However, current liquid-propellant oxidizers are generally selected from such materials as nitric acid, hydrogen peroxide or-Iiquid oxygen; the dangerous characteristics of which materials are well known and constitute major objections.

It has been found that the disadvantages resulting from the dangerous characteristics of such liquid-propellant oxidizers and the many problems inherent in the employment of solid fuel systems in reaction propulsion motors are eliminated by the new and improved fuel system formulations wherein the liquid-propellant oxidizers comprise water, methanol, and magnesium nitrate or aluminum nitrate. Such liquid-propellant oxidizers may be very advantageously employed in reaction propulsion motors where the fuel is a light metal such as magnesium, lithium, aluminum or boron, or combinations of such light metals, preheated to a reactive state as to be more fully described hereinafter.

The advantages of the liquid-propellant formulations of the present invention are high performance in rocket applications, low-freezing point, high density, and unusually safe handling characteristics.

In the utilization of the present invention to produce thrust in rockets a suitable liquid mixture of water, methanol and either magnesium nitrate or aluminum nitrate is maintained in a container within the rocket body. In selecting the particular mixture of these materials for use in a given application, consideration should be given to the temperatures specified for storing the rocket. Here an extreme range is available for these new oxidizers ture compressed into briquettes.

3,152,937. Patented Get. i3, l'964 since many formulations that freeze below either -30 F. or 65 F. and boil above F. are available;

these temperatures being the extremes normally encountered in rocket applications. In FIGS. 2 and 3 the formulations included within the areas to the right of curves x and y fulfill those physical requirements. A specific formulation in this boundary having excellent physical properties with freezing point well below 65 F. and providing .very good performance is 35% H O-45% CH OH and 20% -Mg(NO and many other satisfactory formulations are available as shown in FIGURES 2 and 3. For example the following mixtures are satisfactory:

Water from about 5 to about 65%, methanol from about 5 to about 65%, and from about 5 to about 35% magnesium nitrate; and

Water from about 15 to about 60%, aluminum nitrate from about 5 to about 30%, and methanol from about 20 to about 70%.

As with any rocket using liquid propellants, a pressurizing or pumping system is employed to convey predetermined amounts of the liquid oxidizer into the reaction chamber. In the case of the propellant system here described, the oxidizer is appropriately injected into the combustion chamber so as to achieve intimate contact with the light metal fuel following which the light metal- "oxidizer mixture undergoes chemical reaction in a typical metal fuel, the light metal should be preheated to a reactive -temperature which in general is a temperature approaching the melting point of the selected metal or metal mixture. For example, satisfactory results are obtained when aluminum is heated to about 660 C., magnesium is heated to about 650 C., and lithium is heated to about 'C.

p The light metal fuels may be brought to reactive temperatures by supplying heat thereto in'many ways, for example:

(1) The light metal may be mixed with a small amount of a solid oxidizer, such as sodium nitrate, and the mix- The solid grain thus formed, when ignited by a flare or the like, will burn with the solid oxidizer reacting chemically with a small por storage tank'by means of electric heaters "or the like;

(3) The light metal in granular form may be brought to reactive temperature by passing it through a heat exchanger that contacts the combustion chamber of the rocket.

After the light metal fuel is heated to its reactive temperature it is sprayed as a gas, liquid or finely-divided solid into contact with the liquid oxidizer. When the solid-grain technique is used for heating the metals (No. 1 above), such a spray is produced automatically on burn ing the grain. 0n the other hand, when the metal is heated to melting temperatures by other means (No. 2 or 3 above), the molten metal may be atomized by means customarily used for liquids.

Very satisfactory rocket performances are obtainedwhen the aforementioned liquid oxidizer (35% H 0, 45% CH OH and 20% Mg(NO is reacted with a fuel consisting of 40% magnesium-40% aluminum-18% sodium nitrate-2% binder such as linseed oil. The latter is compressed into a briquette and acts as described in item 1.

The above disclosed system operating at about 1700 p.s.i.a. chamber pressure has a specific impulse of 232 pounds of thrust per pound per second of propellant flow and a density of 1.481 grams per cubic centimeter. Thus, the density-impulse, which is defined as specific impulse multiplied by density and is generally accepted as a measure of the performance potential of a propellant, is 344. The well-known competent rocket propellant combination of red fuming nitric acid and hydrazine also has a density impulse of 344 at the same operating pressure of 1700 p.s.i.a. Thus, in many applications the performances of these two systems are equivalent.

The light metal fuel may comprise all aluminum, magnesium, lithium or boron, or mixtures of one of more of these metals, with or without suitable binders and solid oxidizers depending on the type of fuel system to be employed in the rocket and as hereinbefore described the means employed for bringing the light metal fuel to a reactive temperature.

Referring to FIG. 1 of the illustrative embodiment of the invention there is shown by way of example a suitable rocket incorporating one of the new and improved propellant formulations hereinbefore described. In FIG. 1, is the outer skin or shell of the rocket having a nose portion 12, a body portion 14, a mixing chamber 16, a combustion chamber 18 and nozzled outlet 20.

The body portion 14 is separated from the mixing chamber 16 by partition 22, the rearward portion of which is shaped as at 24 to direct the liquid oxidizer issuing from nozzled outlets 25 into contact with the light metal fuel as to be more fully described.

The body portion of the rocket is divided into concentric chambers 26 and 28 by cylindrical wall 30 which extends forwardly from the partition member 22. As shown in the drawing the upper end of wall 30 terminates short of the nose portion 12 of the rocket and is provided with a closure member 32 having a restricted opening 34 therethrough.

Between the inner surfaces of wall 30 and between the member 32, and partition member 22, is secured a division member 36 having a restricted opening 38 therethrough; the opening 38 being smaller than the opening 40 in partition 22.

Between the outer surface of wall member 30 and the inner surface of the shell of the body of the rocket is provided an annular piston 42 provided with suitable seals or piston rings 44.

The rocket described above is fueled and readied for flight as follows:

A predetermined mixture of a liquid oxidizer as disclosed herein is placed in chamber 28; a light metal-solid oxidizer briquette 46 is placed in chamber 26 between divider 36 and partition 22; a small charge 48 such as a solid rocket grain or black powder provided with a conventional electric squib or ignitor 50 is placed in cham- 4 her 26 between the top plate 32 and divider 36; and an electric squib or ignitor 52 of conventional design is placed in combustion chamber 18.

To operate the rocket squibs and 52 are activated. Squib 50 ignites charge 48 which produces heat to ignite the solid fuel-solid oxidizer briquette 46 and at the same time produces gas for pressurizing the liquid oxidizer in chamber 28.

The pressure produced by charge 48 forces the piston 42 rearwardly which in turn forces the liquid oxidizer through nozzles 25 into the mixing chamber 16.

Simultaneously reaction at the surface of the fuel briquette 46 occurs between the light-metal fuel and the solid oxidizer which melts the adjacent light-metal fuel and vaporizes a portion of it, which action causes the metal to issue through opening 40 into the mixing chamber 16.

The light metal fuel-liquid oxidizer mixture is ignited by flare 52- and reacts in the combustion chamber to produce rocket thrust as shown by the flow arrows.

From the foregoing description of my invention, ineluding specific apparatus embodying the invention, it will be seen that the aims, objects and advantages set forth herein are fully accomplished; and I claim as my invention the following:

1. An oxidizer for a light metal fuel selected from the group consisting of magnesium, aluminum, lithium, and boron, said oxidizer consisting essentially of a liquid mixture of from about 15 to about percent water, of from about 5 to about 35 percent magnesium nitrate and from about 5 to about 65 percent methanol.

2. An oxidizer for a light metal fuel selected from the group consisting of magnesium, aluminum, lithium, and boron, said oxidizer consisting essentially of a liquid mixture of from about 15 to about 60 percent water, of from about 5 to about 30 percent aluminum nitrate and from about 20 to about percent methanol.

3. An oxidizer for a light metal fuel selected from the group consisting of magnesium, aluminum, lithium, and boron, said oxidizer consisting essentially of a liquid mixture of from about 15 to about 60 percent water, from about 5 to about 30 percent methanol and the remainder a nitrate selected from the group consisting of aluminum nitrate and magnesium nitrate.

References Cited in the file of this patent UNITED STATES PATENTS O'Neill Aug. 26, 1924 Maxim Oct. 21, 1924 OTHER REFERENCES 

1. AN OXIDIZER FOR A LIGHT METAL FUEL SELECTED FROM THE GROUP CONSISTING OF MAGNESIUM, ALUMINUM, LITHIUM, AND BORON, SAID OXIDIZER CONSISTING ESSENITALLY OF A LIQUID MIXTURE OF FROM ABOUT 15 TO ABOUT 65 PERCENT WATER, OF FROM ABOUT 5 TO ABOUT 35 PERCENT MAGNESIUM NITRATE AND FROM ABOUT 5 TO 65 PERCENT METHANOL. 